The present invention relates to an improved method of repairing a subsea pipeline which involves pressure forming the end of a section of pipe into an annular connection member so that connection can be made to the pipe. The repair of subsea pipelines has been accomplished by the use of equipment manipulated from the surface and by direct manipulation of divers at the subsea location.
Normally a section of a pipeline is damaged or ruptured and such section is first cut from the pipeline by suitable apparatus at the subsea location. Thereafter it is necessary to prepare the cut ends of the pipeline for attachment to a replacement section of pipe which will be lowered to the subsea location and positioned between the open ends of the pipeline to replace the damaged section.
U.S. Pat. No. 4,662,663 to T. R. Schmitz discloses apparatus and method of providing the connection to the end of a subsea pipeline after the damaged section has been removed. Generally, such patent suggests that a tool be positioned within the end of the pipeline and the annular connector be positioned around the end of the pipeline and pressure be supplied to the tool to pressure form the end of the pipeline into tight sealing and gripping engagement with the interior of the connecting tool. Similar types of pressure forming is suggested in U.S. Pat. Nos. 3,432,916, and 4,388,752. Also, copending applications Ser. No. 07/098,197, filed Sept. 28, 1987 and Ser. No. 07/114,422, filed Nov. 28, 1987 have been directed to forming tools for pressure forming of tubular members within a well bore into surrounding annular members.
While such methods have been used, some difficulties have been encountered with their use in a subsea location. One difficulty is that it is a problem to mount the forming tool on a suitable frame and move it into the desired position with respect to the end of the pipeline which is to be deformed. A further problem encountered is that most subsea pipelines are at least partially embedded in the earth of the sea floor and the movement of the tool and the surrounding annular connector into position within and surrounding the open and of the pipeline has caused sand and other subsea floor detritus to enter into the interior profile of the annular connector. This presence of sand or other solid materials within the connector profile can prevent the formation of a proper sealing and gripping engagement with the end of the pipeline.